Long running task in workflow foundation 4

Question

I have an application in which there are long running process, to handle that i have used Windows Workflow4

Process depends on number of users If number of users are less ie 30-100 then it is working fine and if greater than 500 then there is problem

My problem is even if the Workflow process is completed View is showing processing but in backend it is completed

Workflow code

WorkflowApplication application;
  application = new WorkflowApplication(new Payroll_Workflow.PayrollProcess(), inputparam);
                application.SynchronizationContext = new SynchronousSynchronizationContext();
                //we assign a delegate for the Completed event of the application
                application.Completed = delegate(WorkflowApplicationCompletedEventArgs completedEvent)
                {
                    if (completedEvent.TerminationException != null)
                    {
                        communicationMessage.message = completedEvent.TerminationException.Message.Replace("_", " ");
                        //ErrorMessages error = (ErrorMessages)Enum.Parse(typeof(ErrorMessages), completedEvent.TerminationException.Message.Replace(" ", "_"));
                    }
                    else
                    {
                        communicationMessage.message = "Process Completed";
                    }
                };

                //we start the application
                application.Run();

Answer 1

Are your workflows all reaching "communicationMessage.message = "Process Completed";" ?

If they are then perhaps this communication process is being overwhelmed?